Designing Missing Tiles

Counting items is not an uncommon mechanic in brain training applications. In A Clockwork Brain, however, the logic is reversed; players have to count what is missing, without being distracted by what is there. This can lead to very interesting gameplay, as the boundaries between the tiles are lost and the border-less shapes that are created become more homogenous and more difficult to process than in a typical count-the-blocks game.

Missing Tiles mini-game from Prototype to Final version


The player sees a grid of tiles. A small number of them is missing, and the rest of the board is fully occupied. The objective is to count the number of tiles that are missing and press the corresponding button at the bottom of the screen.

The mechanics are deceptively simple, but the there are several attributes that create a quite challenging game.

Difficulty & Progression

Difficulty progression in Missing Tiles

Easy, medium, hard and insane difficulty progression in Missing Tiles

The difficulty parameters are the following:

  • Grid size: the game starts with 6×6 large tiles and ends up displaying 12×12 tiles, much smaller in size.
  • Number of missing blocks: starting off with as few as 2, going up to 15-16 tiles.
  • Clustering: the number of clusters of missing tiles affects the difficulty; larger clusters are more difficult to process, more clusters need more time for calculating their sums.
  • Tile shape: square tiles are generally easier to count than rectangular ones.
  • Number of options: the player may choose from 3, 4, or 5 options, which display the number of missing tiles on the board; the fewer the options, the easier it is to evaluate them.
  • Mixed textures: most levels display one type of tile material, but in later stages the player may see more than one tile type at the same time; this creates some noise, which makes it harder for the brain to process.
  • Alignment: in later stages the tiles are not stacked perfectly one above the other; every other line there is a horizontal offset on all tiles, which makes the pattern somewhat irregular and harder to read.


Missing Tiles trains spatial cognition and visual perception, as well as calculation. Players have to count the number of similar or identical items, arranged in a grid. This is different than most mini games that ask players to count tiles, because the logic is reversed; players have to count something that is not there, based on its outline or silhouette.

Simple shapes

Common patterns are typically processed by the brain without having to manually count each tile

Pattern matching is the first step. The missing blocks create shapes of black rectangles or squares. Very often these shapes are very easy to identify; a single tile, 2 adjacent tiles, 4 tiles forming a square, 5 tiles forming a cross and so on. These are much faster to identify than more complex shapes.

The complex, irregular shapes are much more difficult to process at once, and often need to be mentally broken down to simpler patterns that can be recognized individually.

Complex shapes

Complex shapes often need to be broken down to simpler ones

Calculation is what comes next. In intermediate and later levels there are various clusters of missing blocks. Players usually count the number of tiles missing in each cluster and add them up together, to find the final answer.

Last but not least, the available choices may allow some players to answer faster. The reason is that they may not have to calculate the full sum of all missing tiles, if some of the choices are obviously too high or too low to be true. Therefore, they can rule out some or all of the choices except one, which would be the right answer.

Insane Round

Levels in the Insane Round have very small tiles, which are always offset, thus not perfectly aligned on top of each other. There are 5 choices, many tiles missing, forming large clusters, which are harder to process, and there are many different types of tiles and materials present on the board.

Offset tiles are harder to process

Hard level (left) and Insane level (right) with offset tiles

You can find this and more mini-games in A Clockwork Brain.

Dimitrios Bendilas
Lead Game Designer
Follow me at @dimitriosb
Total Eclipse is @TEGames